I don't know if this is something new with iphone OS 3.0 or not, but I just stumbled upon it and thought i'd share. I recently extended my ipod cable and put the cable for it coming up into the cabin. I've noticed that even if the "Accessory Connected" screen is up on the iphone, you can hit the iphone home button to get back to the home screen, and then fire up pandora like you normally would. It fades out the music playing and starts pandora. Volume steering wheel controls work, but the radio display shows the name of whatever mp3 was playing from your ipod before you started pandora.

I was always of the opinion you couldn't get past that accessory connected screen, but i guess something changed in OS 3.0? For the record: iPhone GS, OS 3.0

 

Did you try this before and it didn't work?